Sa'id bin Abi Maryam سعيد بن أبي مريم · The Book of Fasting

"while we were with the Messenger of Allah, sitting in the Masjid, a man entered on a camel. He made it kneel in the Masjid, then he hobbled it. Then he said; 'Which of you is Muhammad?' He was reclining among them, and we said to him: 'This white man who is reclining.' The man said to him: 'O son of 'Abdul-Muttalib.' The Messenger of Allah said to him: 'I have answered you.' The man said: 'O Muhammad, I am…

"The Messenger of Allah said: 'Whoever among you can afford to get married, let him do so, and whoever cannot afford it should fast, for it will be a restraint (Wija) for him."'